Project Summary/Abstract A third of low-income US households experience food insecurity, which increases the risk for multiple health problems and is associated with increased healthcare expenditures and utilization. The Supplemental Nutrition Assistance Program (SNAP, formerly the ?Food Stamp Program?) has been shown to reduce (but not eliminate) food insecurity. Notably, SNAP is disproportionately utilized by people with disabilities, who have heightened exposure and sensitivity to food insecurity and elevated healthcare costs. People with chronic illnesses are also especially sensitive to food insecurity and changes in SNAP benefits. It follows that changes in SNAP policies would affect healthcare expenditures and utilization, particularly for people with disabilities and chronic illnesses. The scarce literature in this area supports this proposition but only consists of ecological studies by our team and two cross-sectional studies. Causal inferences from these studies were limited. We propose to assess the potential causal relationships between SNAP and healthcare expenditures and utilization, hypothesizing that SNAP reduces healthcare expenditures and utilization (Aim 1) and that such effects are heightened for people with disabilities and chronic illnesses (Aim 2). We will link 2012-2016 data from the Massachusetts (MA) All-Payer Claims Database, the MA Department of Transitional Assistance (which operates SNAP in the state), the MA Medicaid program, and the MA Department of Public Health, yielding uniquely detailed longitudinal data. We will have in-depth SNAP information for recipients, as well as data on expenditures, utilization, disability, chronic conditions, and demographics for recipients and non- recipients. We will exploit technical errors that led to 43,000 out of 449,000 MA SNAP-recipient households arbitrarily receiving wrongful termination notices in 2014-2015. Of these, about a third never regained benefits, and about two-thirds lost benefits but eventually had them reinstated. The resulting complete (100%) losses and reinstatements of benefits represent significantly larger shocks than the 5.5% or 13.6% changes in benefit levels studied previously, with effects likely magnified for people with disabilities and chronic illnesses. We will use growth curve models with interrupted time series design elements to assess the effects of the SNAP terminations and reinstatements on healthcare spending and utilization patterns in the MA Medicaid population (Aim 1), and we will assess how disability and chronic illness status moderated any such effects (Aim 2). Social welfare programs such as SNAP affect key determinants of health, but study of their effects on healthcare is nascent. Our analyses will inform health systems as they develop methods to improve outcomes and reduce costs by addressing the social determinants of health, thereby aligning with AHRQ?s priority to improve health care affordability and efficiency.